The book was written careful observations and detailed studies.
A. on behalf of
B. regardless of
C. on the basis of
D. in relation of
网友回答
A. on behalf of
B. regardless of
(答案→)C. on the basis of
D. in relation of
解析：A. on behalf of代表，B. regardless of不管，不顾，C. on the basis of在…基础上，D. in relation of关于，句意：这本书是在仔细的观察和详细的研究的基础上写的。根据句意选C。